Monitoring of various public places, business premises and private homes is becoming increasingly important as they contain increasingly valuable equipment, both of economic value, such as expensive computer equipment, and sentimental value, such as family heirlooms.
In order to meet these increased monitoring needs, there are different types of monitoring systems. One type of monitoring system according to prior art normally comprises a monitoring station and a number of monitoring modules, each of which monitors a monitored location. Each monitoring module is connected to a monitoring station via communication cables. Traditionally, a monitoring module is a video camera which continually records images which are transmitted to the monitoring station. In the monitoring station there are one or more alarm operators, who watch the transmitted images to decide whether any unauthorized activity is taking place, such as a burglar appearing at the monitored location. The disadvantage of this system is that the alarm operators must be paying attention continuously if there is anyone in the transmitted images. This severely limits the number of monitoring modules that can be connected to the monitoring station, which also results in the monitoring being very expensive. In order to reduce the quantity of images transmitted to the monitoring station, the monitoring module comprises a video camera and an infrared detector which are connected to each other. When the infrared detector detects a movement, a video recording is started. The video images can be transmitted via the communication cables to the monitoring station where an operator views the images and makes a decision regarding measures to be taken. A problem with this type of monitoring system is that in many cases the recorded images do not provide sufficient information about what has caused the alarm. This can occur when, for example, alarm situations, detected by the infrared detector, which have been caused by high temperatures or sabotage are not caught by the camera. In addition, the system still transmits a relatively large quantity of data.
Patent application WO 98/28706 describes a monitoring system which comprises a number of cameras that are connected to a monitoring station. The cameras record images that are transmitted to the monitoring station. The monitoring station processes the images to determine whether there is an alarm situation or not. If it is determined that there is an alarm situation, an alarm signal is forwarded.